Centering work on a rotab

Varga Knives

Varga Knives

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Aug 12, 2006
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I'm probably going about this wrong so I'm open to even the obvious.

I have a rotary table which I centered on my mill using and indicator. My goal is to precisely cut a stop pin arc in a folder. My old way was not precise so that's why I bought the indicator.

My question is how do I actually center the blade? I don't have a chuck on the rotab if that means anything. All I want to go do is clamp the blade to the rotab but do that using the indicator and not just chuck a 1/4" whatever in my mill through the pivot hole. Using the indicator and sliding around the blade on the table and trying to lock it down can't be the right way.

Thanks!
Mark
 
Never done exactly what you are talking about on a mill. If I am correct in assuming this, this is for a production knife? The same blade over and over? If so, I would make a fixture that mounts to the table the blade gets set in the fixture and clamped to the fixture. This would produce very easy repeat ability. That's how I used to manufacture production air ride hitch parts anyways.
 
Definitely a good idea to fixture for production runs but mine are one at a time.

I was thinking about chucking a 1/4" rod and fitting it to the pivot then clamping it down tight. Switch out the rod with the indicator and keep switching back and forth until it's good. Seems like there should be a better way, though.

Truth be told, the precision of the arc isn't all that important. I'm sure I can get it just fine with the rod method. What I'd like is a better process for counterboring bearing pockets and such as well as the arc.
 
Mark, you definitely know a lot more about this stuff than me, but have you ever thought about plunge cutting your bearing pocket with an end mill.
Mike Nguyen (Pittknife) gave me the way he did it and the appropriate size endmill and it works like a charm.
I center it with a 3/16 reamer (upside down), clamp the blade down, take out the collet and replace it with the altin endmill and plunge cut using my dro.

I don't know about the arc though, I haven't milled one yet. I've been using washers until I get a rotary table.
 
Hey Josh. I've made 20ish folders that way and I might stick with it. The way it's "supposed" to be done for precision work is to use a smaller sized endmill and work your way out to the final diameter and depth while turning the rotab. Or at least something like that. Haven't messed around with too much of this side of it yet.
 
Ok. So I just used the rod to center the blade pivot on the rotary table. I switched out the rod for the indicator and ran it. It came to variance of .0011. The rotab was indicated to .0001. If I combine the two I think I could be off center by as much as 12 ten thousandths of an inch. I think that should be good enough. 😁
 
I don't do a lot of hidden pin tracks but when I do, I clamp a pivot in the three jaw chuck on my rotab then drop a shim, the blade, a washer and then the pivot screw and tighten. If I didn't have a 3-jaw, I would turn down a registration pin that fits in the center hole of the faceplate. I locate my start and end points by spot drilling through the liner and then through drilling the blade before putting it on the rotab. After that, I'm just connecting the dots and aligning the rotary table to the spindle is not critical.

Bob
 
Thanks Bob. Similar to the way I do it but accounting for what equipment I have. If I had a lathe I would have made a registration pin/plug but as it is I register off the quill.

I guess there's no perfect way to do it but it seems to be pretty acurate.
 
For the rotary table there are many ways to do it. The quickest way I've found is to use pin gauges to match my location through the rotary table chuck I have and the chuck on my mill. If you don't have a chuck on the rotary table make an insert with the right taper and use that.


About the cb, unless you have a really good dro it's hard and very tedious to do the rotary table cut. I get the same results and dead on with my endmill setup. The best would be to get custom CB made but last couple times for 3/8 CB they would run me $300 each with a minimum of 10 ordered..... So I'm not doing that to get me that last .0005" lol. My mill isn't even that accurate lol
 
I think I need some sort of chuck on my rotab.

Mike, could you explain how your clamp but works and the parts you need for it. It looks like you have a great set up.
 
Varga Knives said:
I think I need some sort of chuck on my rotab.

Mike, could you explain how your clamp but works and the parts you need for it. It looks like you have a great set up.
Click to expand...


I use a 6" phase II rotary table with a mt3 taper on an er25 quick change collet system. I have the exact same for my chuck on my mill. My clamps are just step clamps I machines some pieces for. Just get the right t slot nut and you can use almost any bracket and bolt.

When I want to do angles I have a tilting rotary table with a 4 jaw chuck, setting this up is trickier because you have to center than move offset. I don't have a dro so I pretty much draw lines and mask off then eyeball but from what all the people that have my knives say it looks dead on.

I've shown a lot of makers the er25 collet system and they all switched and love it.

They come in all tapers and at worst just nod a shank to fit your rotary table center taper.
 
Thanks Mike! I have the same table and will pick up an ER to fit. Not sure about the rest of the stuff but I'll figure it out.
 
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